The present invention relates to a method for electrically isolating two circuits from one another while transmitting data between the two circuits. Well known methods include using a transformer, an optical isolator, or a capacitor connected in series on the data line between the two circuits, which will also be referred to herein as a capacitively coupled interface. One disadvantage with using transformers and optical isolators is that they are much more expensive than capacitors. A capacitively coupled interface has successfully been used to transmit analog data between two circuits, however the capacitor decreases the quality of the signal. Digital data in the form of fixed voltage levels can be transmitted over a capacitively coupled interface, however the integrity of the data can be compromised if certain precautions are not taken.
It is accordingly an object of the invention to provide a method of using a capacitively coupled interface to transmit digital data between two electrically isolated circuits wherein the method includes steps for protecting the integrity of the digital data.
It is accordingly an added object of the invention to provide a method of using a capacitively coupled interface to increase the integrity of digital signals transmitted across the interface, which comprises: transmitting signals between a first electronic circuit and a second electronic circuit using a capacitively coupled interface; and protecting the integrity of the signals by using a protocol.
In accordance with an additional feature of the invention, the method includes transmitting a signal from a first electronic circuit to a second electronic circuit on a capacitively coupled interface; after the second electronic circuit receives the signal from the first electronic circuit, transmitting a unique synchronization sequence from the second electronic circuit to the first electronic circuit on the capacitively coupled interface; constructing a status signal that contains information concerning a status of the first electronic circuit; after the first electronic circuit receives the unique synchronization sequence, transmitting the status signal and a data signal from the first electronic circuit for reception by the second electronic circuit on the capacitively coupled interface; determining if the received status signal corresponds to a predetermined status signal; and if the received status signal corresponds to the predetermined status signal, determining that the received data signal is valid.
In accordance with an another feature of the invention, the method includes: after the second electronic circuit receives the signal from the first electronic circuit and before performing the step of transmitting a unique synchronization sequence from the second electronic circuit to the first electronic circuit on the capacitively coupled interface, sending a clock signal from the second electronic circuit to the first electronic circuit on the capacitive interface.
In accordance with a further feature of the invention, the method includes performing the step of transmitting the signal from the first electronic circuit to the second electronic circuit on a first capacitively coupled channel; and performing the step of transmitting the unique synchronization sequence from the second electronic circuit to the first electronic circuit on a second capacitively coupled channel.
In accordance with an added further feature of the invention, the method includes: after the second electronic circuit receives the signal from the first electronic circuit and before performing the step of transmitting a unique synchronization sequence from the second electronic circuit to the first electronic circuit on the second capacitively coupled channel, sending a clock signal from the second electronic circuit to the first electronic circuit on a third capacitive channel.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method of using a capacitively coupled interface to increase the integrity of digital signals being transmitted across the interface, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.